Heterosubtypic Neutralizing Monoclonal Antibodies Cross-Protective against H5N1 and H1N1 Recovered from Human IgM+ Memory B Cells

Abstract

BackgroundThe hemagglutinin (HA) glycoprotein is the principal target of protective humoral immune responses to influenza virus infections but such antibody responses only provide efficient protection against a narrow spectrum of HA antigenic variants within a given virus subtype. Avian influenza viruses such as H5N1 are currently panzootic and pose a pandemic threat. These viruses are antigenically diverse and protective strategies need to cross protect against diverse viral clades. Furthermore, there are 16 different HA subtypes and no certainty the next pandemic will be caused by an H5 subtype, thus it is important to develop prophylactic and therapeutic interventions that provide heterosubtypic protection.Methods and FindingsHere we describe a panel of 13 monoclonal antibodies (mAbs) recovered from combinatorial display libraries that were constructed from human IgM+ memory B cells of recent (seasonal) influenza vaccinees. The mAbs have broad heterosubtypic neutralizing activity against antigenically diverse H1, H2, H5, H6, H8 and H9 influenza subtypes. Restriction to variable heavy chain gene IGHV1-69 in the high affinity mAb panel was associated with binding to a conserved hydrophobic pocket in the stem domain of HA. The most potent antibody (CR6261) was protective in mice when given before and after lethal H5N1 or H1N1 challenge.ConclusionsThe human monoclonal CR6261 described in this study could be developed for use as a broad spectrum agent for prophylaxis or treatment of human or avian influenza infections without prior strain characterization. Moreover, the CR6261 epitope could be applied in targeted vaccine strategies or in the design of novel antivirals. Finally our approach of screening the IgM+ memory repertoire could be applied to identify conserved and functionally relevant targets on other rapidly evolving pathogens.

Influenza virus A(H1N1)2009 antibody-dependent cellular cytotoxicity in young children prior to the H1N1 pandemic

“…Notably, the highest induction of ADCC in response to HA1 or the HA trimer was detected in the pre-pandemic samples (#3 and #51, Fig. 5 Several studies have shown pre-existing immunity against A(H1N1)2009 in adults (Corti et al, 2010(Corti et al, , 2011Ekiert et al, 2009;Throsby et al, 2008), whereas little or no preexisting cross-reactive antibodies were detected in a group of 124 children aged 6 months to 9 years (Hancock et al, 2009) the HA2 domain, which is not presented in our array (Greenbaum et al, 2009;Li et al, 2012).…”

“…Persons born before the 1940s were most protected against the A (H1N1)2009, which has been related to the similarity between the HA1 of the 1918 and 2009 pandemic strains Xu et al, 2010); however, some protection was also observed in younger adults. Cross-neutralizing antibodies have been implicated in this immune protection, possibly resulting from the boosting of antibodies that had developed against previous seasonal strains ( Corti et al, 2010Corti et al, , 2011Ekiert et al, 2009;Li et al, 2012;Throsby et al, 2008;Wrammert et al, 2011). However, cross-reactive antibodies were hardly detected among children aged 6 months to 9 years (Hancock et al, 2009).…”

IFN-γ–Producing CD4+ T Cells Promote Generation of Protective Germinal Center–Derived IgM+ B Cell Memory against Salmonella Typhi

“…Interestingly, human IgM + memory B cells can produce neutralizing Abs against existing and extinct influenza virus species, thus providing efficient cross-protection (48). Notably, the major proportion of CD27 + memory B cells in human blood expresses IgM (49), and BCL-6 mutation analysis suggests that these cells are derived from a T cell-dependent GC reaction (50).…”

Cross-Protection of Chicken Immunoglobulin Y Antibodies against H5N1 and H1N1 Viruses Passively Administered in Mice

“…It has been reported that there exist highly conserved epitopes in the stem region of the HA molecule that may become a target for a "universal flu vaccine" (3,7,10,14,15). Humanized monoclonal antibodies raised against these conserved epitopes from a single influenza virus strain were shown to provide strong cross-protection against heterologous strains (13).…”